Stator, method for manufacturing stator, and motor

ABSTRACT

A stator includes: a stator core having an annular portion and a plurality of teeth that is radially protruded outward from an outer periphery of the annular portion; a molded coil that has an air-core portion into which the teeth of the stator core are inserted and that is stored in a slot formed between the teeth of the stator core; and a yoke that covers a circumference of the molded coil stored in the slot of the stator core. The molded coil has an arc-shaped cross-section, and the molded coil includes a resin-molded portion and an exposed portion exposed at the molded portion.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application Nos.2014-25927 filed on Feb. 13, 2014 and 2014-242214 filed on Nov. 28, 2014with the Japan Patent Office, the entire content of which are herebyincorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a stator for a motor, a method formanufacturing the stator, and a motor, with use of resin molded coils.

2. Description of the Related Art

There is a stator core with a slot-type outer shape. In the stator corewith the slot-type outer shape, a plurality of teeth is radiallyprotruded outward from the outer periphery of an annular portion. Thatis, the stator core has slots between the teeth on the outer side of theannular portion.

An air-core coil with a hollow air-core portion at the center is usedfor the stator core. The air-core coil is generally resin-molded in aresin molding die and formed as a molded coil.

The molded coil is stored in the slot. The air-core portion of themolded coil is inserted into each of the teeth protruded from the outerperiphery of the annular portion of the stator core.

There has been disclosed a ring-shaped stator as a technique related toa stator with molded coils (see Japanese Patent No. 4910089). In thering-shaped stator, the molded coils are resin-molded in resin moldingdies, for example. The molded coils are trapezoidal in cross-section andhave hollow portions. The molded coils are inserted into teeth protrudedfrom the outer peripheral portion of the stator core and are fitted intoa yoke. According to the technique disclosed in Japanese Patent No.4910089, there is no need for insulating work to be performed on membersother than the molded coils or providing an insulating structure,thereby reducing the manufacturing cost.

SUMMARY

A stator includes: a stator core having an annular portion and aplurality of teeth that is radially protruded outward from an outerperiphery of the annular portion; a molded coil that has an air-coreportion into which the teeth of the stator core are inserted and that isstored in a slot formed between the teeth of the stator core; and a yokethat covers a circumference of the molded coil stored in the slot of thestator core. The molded coil has an arc-shaped cross-section, and themolded coil includes a resin-molded portion and an exposed portionexposed at the molded portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an entire configuration of a motoraccording to an embodiment;

FIG. 2 is a perspective view of an air-core coil before moldingaccording to the embodiment;

FIG. 3 is a perspective view of the air-core coil after moldingaccording to the embodiment;

FIG. 4 is a perspective view of a molded coil according to theembodiment;

FIG. 5 is a perspective view illustrating a state in which the moldedcoils are attached to a stator core according to the embodiment.

FIG. 6 is a perspective view of a stator according to the embodiment;

FIG. 7 is a perspective view of an attachment structure of the statoraccording to the embodiment;

FIG. 8 is a diagram for describing a process for a method formanufacturing the stator according to a first embodiment;

FIG. 9 is a diagram for describing a process for a method formanufacturing the stator according to a second embodiment;

FIG. 10 is a perspective view of a coil after first resin molding in thestator according to the second embodiment;

FIG. 11 is a perspective view of the coil after second resin molding inthe stator according to the second embodiment;

FIG. 12 is a diagram for describing a process for a method formanufacturing the stator according to a third embodiment;

FIG. 13 is a schematic view of a conventional stator with three slotsand three coils;

FIG. 14 is a schematic view of a conventional stator with six slots andthree coils; and

FIG. 15 is a schematic view of a conventional stator with six slots andsix coils.

DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, for purpose of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the disclosed embodiments. It will be apparent,however, that one or more embodiments may be practiced without thesespecific details. In other instances, well-known structures and devicesare schematically shown in order to simplify the drawing.

According to the technique disclosed in Japanese Patent No. 4910089, inthe case where the number of magnetic poles of the stator core isreduced to three or six, for example, when the trapezoidal molded coilsare stored in the slots, dead spaces are produced in the slots. The deadspaces in the slots naturally lead to reduction in coil density, andthus reduction in motor efficiency.

An object of the present disclosure is to provide a stator that has asimple structure, improves coil density in slots, and enhances motorefficiency, a method for manufacturing the stator, and a motor includingthe stator.

A stator according to an embodiment of the present disclosure includes:a stator core having an annular portion and a plurality of teeth that isradially protruded outward from an outer periphery of the annularportion; a molded coil that has an air-core portion into which the teethof the stator core are inserted and that is stored in a slot formedbetween the teeth of the stator core; and a yoke that covers acircumference of the molded coil stored in the slot of the stator core.The molded coil has an arc-shaped cross-section, and the molded coilincludes a resin-molded portion and an exposed portion exposed at themolded portion.

In addition, a motor according to an embodiment of the presentdisclosure includes: the above-described stator; a shaft that ispivotally supported in the stator in a rotatable manner; and a rotorthat is stored in the stator to be spaced from the stator and is fixedto a circumference of the shaft. The rotor has a rotor core and aplurality of permanent magnets that is arranged on a surface or insideof the rotor core.

Further, a method for manufacturing a stator according to an embodimentof the present disclosure includes: bending an air-core coil with anair-core portion to have an arc-shaped cross-section; forming a moldedcoil with the air-core portion by resin-molding the air-core coil suchthat tip portions thereof are exposed; inserting a plurality of teeth ofa stator core with an annular portion and the teeth radially protrudedoutward from an outer periphery of the annular portion into the air-coreportion of the molded coil to store the molded coil in a slot formedbetween the teeth of the stator core; and covering with a yoke themolded coil stored in the slot of the stator core.

According to the embodiment of the present disclosure, it is possible toprovide a stator and a motor that have a simple structure and that allowincrease of coil density in the slots by reducing dead spaces in theslots and enhancement of motor efficiency.

A stator, a method for manufacturing the stator, and a motor includingthe stator according to the embodiment will be described below withreference to the accompanying drawings.

In the stator, the method for manufacturing the stator, and the motoraccording to the embodiments, the air-core coil is formed in such amanner that its cross-section is arc-shaped (i.e., the air-core coil hasan arc-shaped cross-section). In the arc-shaped air-core coil, the tipportion of a conductive pin is exposed. The entire air-core coil (exceptfor the tip portion of the conductive pin) is resin-molded.

Therefore, according to the embodiment, it is possible to provide astator that has a simple structure and that allows increase of coildensity in slots by reducing dead spaces in the slots and enhancement ofmotor efficiency, and a motor including the stator.

[Configuration of Motor and Stator]

First, a configuration of the motor according to the embodiment will bedescribed with reference to FIGS. 1 to 7. FIG. 1 is a schematic view ofan entire configuration of the motor according to the embodiment FIG. 2is a perspective view of an air-core coil before molding according tothe embodiment. FIG. 3 is a perspective view of the air-core coil aftermolding according to the embodiment. FIG. 4 is a perspective view of amolded coil according to the embodiment. FIG. 5 is a perspective viewillustrating a state in which the molded coils are attached to a statorcore. FIG. 6 is a perspective view of a stator according to theembodiment. FIG. 7 is a perspective view of an attachment structure ofthe stator according to the embodiment.

The motor according to the embodiment may be an AC servo motor, forexample.

As illustrated in FIG. 1, a motor 100 includes a stator 2 and a rotor 3in a bracket (not illustrated).

The bracket is composed of a load side bracket and a non-load sidebracket. In the bracket, a columnar space is defined to accommodate thestator 2 and the rotor 3. The bracket has a through hole (notillustrated) at both ends for insertion of a shaft 4. The shall 4 ispivotally supported in a rotatable manner in the stator 2, for example.

The material for the bracket may be a soft magnetic body such as asilicon steel plate or an aluminum alloy, for example. However, thematerial for the bracket is not limited thereto.

The stator 2 is fixed to the inner peripheral surface of the load sidebracket. The stator 2 has a yoke 10, a stator core 20, and coils 30.

The yoke 10 is a cylindrical metallic member provided along the innerperipheral surface of the bracket. The yoke 10 surrounds thecircumference of the coils 30 stored in the stator core 20. The yoke 10has the function of closing a magnetic line of force and maximizing theaction of electromagnetic induction. The yoke 10 also has the functionof preventing or suppressing the impact on peripheral devices of themotor 100 by a magnetic field resulting from electromagnetic induction.

The material for the yoke 10 may be a soft magnetic body such as asilicon steel plate, for example. However, the material for the yoke 10is not limited thereto.

The stator core 20 is a deformed cylinder-shaped magnetic member. Thestator core 20 has an annular portion 21 and a plurality of teeth 22.The teeth 22 are radially protruded outward from the outer periphery ofthe annular portion 21 of the stator core 20. Slots 23 are defined andformed as spaces to accommodate the coils 30 between the teeth 22 and22.

The material for the stator core 20 may be a soft magnetic body such asa silicon steel plate as in the case of the yoke 10, for example.However, the material for the stator core 20 is not limited thereto.

Each of the coils 30 of the embodiment is a resin-molded coil with anair-core portion 31 (see FIG. 2). The cross-section of the coil 30 isarc-shaped. The coil 30 of the embodiment is formed as described below.

First, as illustrated in FIG. 2, an air-core coil 30 a is wound with useof a winding frame (not illustrated). The air-core coil 30 a is shapedlike a rectangular frame and has the hollow air-core portion 31 at thecenter. The electric wire of the air-core coil 30 a is formed by asquare wire with a rectangular cross-section. That is, the electric wireof the air-core coil 30 a includes the square wire with a rectangularcross-section.

Conductive pins 32 and 32 are brazed to a winding start portion and awinding end portion of the air-core coil 30 a (equivalent to a windingstart and a winding end of the molded coil 30 (described later)). Theshape of the conductive pin 32 is not limited to a circular column as inthe embodiment. The shape of the conductive pin 32 may be any othershape such as a flat plate or a square column.

Next, as illustrated in FIG. 3, the air-core coil 30 a is molded in amolding die (not illustrated) in such a manner that its cross-section isarc-shaped. That is, the air-core coil 30 a has an arc-shapedcross-section.

Further, the arc-shaped air-core coil 30 a is fixed to anelectrically-insulating bobbin (not illustrated). The bobbin is made ofa synthetic resin, for example. However, the material for the bobbin isnot limited thereto but may be any other material with electricalinsulation properties. The arc-shaped air-core coil 30 a fixed to thebobbin is arranged in a resin molding die (not illustrated) while thetip portions of the conductive pins 32 and 32 are exposed. Then, theentire air-core coil 30 a (except for the tip portions of the conductivepins 32 and 32) is molded of a synthetic resin (molding resin).

The molding resin may be an epoxy resin, for example. However, themolding resin is not limited thereto. The material for the bobbin andthe material for the molding material may be the same or different fromeach other.

When the air-core coil 30 a is resin-molded, the resin-molded coil(hereinafter simply referred to as a “molded coil”) 30 is completed asillustrated in FIG. 4. The tip portions of the conductive pins 32 and 32are exposed at one longitudinal end of the molded coil 30. That is, theair-core coil 30 a is resin-molded in such a manner that its tipportions (for example, the tip portions of the conductive pins 32 and32) are exposed. The molded coil 30, as the resin-molded air-core coil30 a, includes a resin-molded portion (the entire the air-core coil 30 aexcept for the tip portions of the conductive pins 32) and an exposedportion that is exposed at the molded portion (for example, the tipportions of the conductive pins 32).

As illustrated in FIG. 5, the molded coils 30 are stored in the slots 23of the stator core 20 (see FIG. 1). At this time, the teeth 22 of thestator core 20 are inserted and arranged in the air-core portions 31 ofthe molded coils 30.

As illustrated in FIG. 6, the molded coils 30 stored on the stator core20 are fitted into the yoke 10.

The number of the slots 23 and the number of the molded coils 30correspond to each other. The illustrated stator 2 is configured to havethree slots and three coils (see FIG. 1). However, the numbers of theslots 23 and molded coils 30 are not limited to the number described inthis embodiment.

A circuit board 40 is disposed at one end of the stator 2. The circuitboard 40 of the embodiment is provided by a printed wiring board. Thecircuit board 40 is brazed to the conductive pins 32 and 32 of themolded coils 30. The circuit board 40 is arranged between the load sidebracket and the non-load side bracket.

The circuit board 40 is fixed to the conductive pins 32 and 32 bybrazing. Therefore, there is a concern that the vibration of the motor100 may separate the brazing material from the conductive pins 32, 32and the circuit board 40.

Thus, as illustrated in FIG. 7, when the stator 2 is attached into abracket 1, the circuit board 40 is preferably fixed by sandwiching anelectrically-insulating elastic body 41 between the non-load sidebracket 1 and the circuit board 40. That is, the stator 2 may includethe electrically-insulating elastic body 41 for fixing the circuit board40 to the bracket 1 between the circuit board 40 coupled to the ends ofthe resin-molded coils (air-core coils 30 a) 30 and the bracket 1.

The material for the electrically-insulating elastic body 41 may benatural rubber, silicon rubber, or urethane, for example. However, thematerial for the elastic body 41 is not limited thereto.

Returning to FIG. 1, the rotor 3 has a rotor core 50 and permanentmagnets 60. The rotor 3 is stored in the stator 2 to be spaced from thestator 2 and is fixed to the circumference of the shaft 4. The shaft 4is rotatably borne by a bearing supported at the both ends of thebracket 1. The shaft 4 constitutes the center of rotation of the rotor3.

The rotor core 50 is a thick cylindrical metallic member provided on thecircumference of the shaft 4. The rotor core 50 may be configured toinclude a rotor core stack with a plurality of laminated core sheets, ormay be configured to include a single thick cylindrical metallic member,for example.

The material for the rotor core 50 may be a soft magnetic body such as asilicon steel plate, for example. However, the material for the rotorcore 50 is not limited thereto.

A plurality of permanent magnets 60 is incorporated (arranged) in asurface or inside of the rotor core 50. The plurality of permanentmagnets 60 is evenly or almost evenly arranged along the circumferentialdirection of the rotor core 50. The plurality of permanent magnets 60 isarranged such that N and S poles are alternately magnetized (placed) inthe circumferential direction of the rotor core 50, for example.However, the magnetization arrangement of the permanent magnets 60 isnot limited thereto.

The permanent magnets 60 may be rare-earth magnets such as neodymiummagnets, for example. However, the material for the permanent magnets 60is not limited thereto. In the embodiment, the air-core coils 30 a areresin-molded such that the tip portions of the conductive pins areexposed. Alternatively, the air-core coil 30 a may be resin-moldedwithout joining (coupling) the conductive pins to the winding startportion and winding end portion of the air-core coil 30 a. For example,the air-core coil 30 a may be resin-molded such that its winding startportion and winding end portion are exposed.

First Embodiment of Method for Manufacturing Stator in SubjectDisclosure

[Operations of Motor and Stator, and Method for Manufacturing Stator]

Next, referring to FIGS. 1 to 8, a method for manufacturing the statoraccording to the embodiment will be described. FIG. 8 is a diagram fordescribing a process for the method for manufacturing the statoraccording to a first embodiment.

The method for manufacturing the stator according to the firstembodiment includes at least the step of molding (for example, bending)the air-core coil and the step of resin-molding the shaped air-core coilto form the molded coil.

Referring to FIG. 8, the method for manufacturing the stator accordingto the first embodiment will be described below in detail.

First, the air-core coil 30 a is wound (step (hereinafter abbreviated as“ST”) 201). The air-core coil 30 a is wound with use of a winding frame(not illustrated), for example. The air-core coil 30 a is wound in theshape of a rectangular frame and has the hollow air-core portion 31 atthe center (see FIG. 2). The electric wire of the air-core coil 30 a(corresponding to the electric wire of the molded coil 30) is formedfrom a square wire with a rectangular cross-section.

Next, the conductive pins 32 and 32 are brazed (ST202). The conductivepins 32 and 32 are brazed to the winding start portion and winding endportion of the air-core coil 30 a, respectively (see FIG. 2).

Then, the air-core coil 30 a is shaped (ST203). Specifically, theair-core coil 30 a is put into a molding die (not illustrated) and isbent such that the cross-section of the air-core coil 30 a is arc-shaped(see FIG. 3). That is, the air-core coil 30 a is shaped in such a mannerthat its cross-section is arc-shaped.

Next, the shaped air-core coil 30 a is resin-molded (ST204). To performthe resin-molding, the arc-shaped air-core coil 30 a is fixed to anelectrically-insulating bobbin (not illustrated). Then, the air-corecoil 30 a with the arc-shaped cross-section fixed to the bobbin is putinto a resin molding die. The entire air-core coil 30 a (except for thetip portions of the conductive pins 32 and 32) is resin-molded while thetip portions of the conductive pins 32 and 32 soldered to the air-corecoil 30 a are exposed. That is, the air-core coil 30 a is resin-moldedsuch that the tip portions of the conductive pins 32 and 32 are exposed.The molding resin may be an epoxy resin, for example.

At ST204, the molded coil 30 with the arc-shaped cross-section iscompleted (see FIG. 4). The tip portions of the conductive pins 32 and32 are exposed at the coil 30.

Next, the molded coils 30 are arranged on the stator core 20 (ST205).The stator core 20 has the plurality of teeth 22 protruded outward fromthe outer periphery of the annular portion 21. The teeth 22 of thestator core 20 are inserted into the air-core portions 31 of the moldedcoils 30 (see FIG. 5). Accordingly, the molded coils 30 are stored inthe slots 23 (defined between the teeth 22 of the stator core 20) on theouter side of the annular portion 21 (see FIG. 1).

Then, the molded coils 30 arranged (stored) on the stator core 20 arefitted into the yoke 10 (the molded coils 30 arranged (stored) on thestator core 20 are covered with the yoke 10) (ST206).

Finally, the circuit board 40 are attached to the molded coils 30(ST207). Specifically, while the circuit board 40 is placed on themolded coils 30, the circuit board 40 is brazed to the conductive pins32 and 32.

After execution of the steps ST201 to ST207, the stator 2 is completed(ST208).

According to the method for manufacturing the stator according to theembodiment, the workability of stator assembly can be improved.

At ST207, the circuit board 40 is fixed by brazing to the conductivepins 32 and 32. Therefore, there is a concern that the vibration of themotor 100 may separate the brazing material from the conductive pins 32,32 and the circuit board 40.

Thus, when the stator 2 is attached into the bracket 1, the circuitboard 40 is preferably fixed by sandwiching the electrically-insulatingelastic body 41 between the non-load side bracket 1 b and the circuitboard 40.

[Operations of Stator and Motor]

Next, referring to FIGS. 1 to 7, the operations of the stator and themotor according to the embodiment will be described.

As illustrated in FIGS. 1 and 7, the motor 100 according to theembodiment has the bracket 1, and the rotor 3 and the stator 2 arrangedin the bracket 1.

In the rotor 3, the plurality of permanent magnets 60 is incorporated inthe surface or inside of the rotor core 50. The plurality of thepermanent magnets 60 is arranged such that the N and S poles arealternately magnetized in the circumferential direction.

Meanwhile, the stator 2 has the plurality of coils 30 that surrounds therotor 3 and aligns in the circumferential direction.

That is, in the motor 100 according to the embodiment, an electriccurrent flows into the coils 30 of the stator 2 to intersect themagnetic flux generated by the permanent magnets 60 on the rotor 3. Inthe motor 100 according to the embodiment, when the magnetic flux of thepermanent magnets 60 and the electric current flowing into the coils 30intersect each other, a circumferential driving force is generated inthe coils 30 by the action of electromagnetic induction to rotate therotor 3 around the shaft 4.

In the stator 2 and the motor 100 according to the embodiment, theair-core coil 30 a is shaped such that its cross-section is arc-shaped.The tip portions of the conductive pins 32 and 32 are exposed at thearc-shaped air-core coil 30 a, and the entire air-core coil 30 a (exceptfor the tip portions of the conductive pins 32 and 32) is resin-molded.By the resin-molding, the molded coil 30 including the conductive pins32 and 32 with the tip portions exposed to the outside is completed.

The molded coils 30 are stored in the slots 23 on the outer side of thedeformed stator core 20. That is, the stator core 20 has the pluralityof teeth 22. The teeth 22 are radially protruded outward from the outerperiphery of the annular portion 21. The spaces surrounded by the teeth22 and 22 on the inner side of the yoke 10 constitute the slots 23.

The slots 23 are widely arc-shaped. Therefore, the arc-shaped moldedcoils 30 can be stored in the slots 23 with few gaps therebetween.Accordingly, dead spaces are not easily produced in the slots 23.According to the manufacturing method of the embodiment, the air-corecoil 30 a is resin-molded while the tip portions of the conductive pinsare exposed. Alternatively, the air-core coil 30 a may be resin-moldedwithout soldering (coupling) the conductive pins to the winding startportion and winding end portion of the air-core coil 30 a. For example,the air-core coil 30 a may be resin-molded while the winding startportion and winding end portion of the air-core coil 30 a are exposed.In this case, the exposed portion of the molded coil 30 is made up ofthe winding start portion and winding end portion of the air-core coil30 a (corresponding to the winding start portion and winding end portionof the molded coil 30).

Second Embodiment of Method for Manufacturing Stator According inSubject Disclosure

Next, a method for manufacturing the stator according to the embodimentwill be described with reference to FIGS. 9 to 11. FIG. 9 is a diagramfor describing a method for manufacturing the stator according to asecond embodiment. FIG. 10 is a perspective view of a coil after firstresin molding in the stator according to the second embodiment. FIG. 11is a perspective view of the coil after second resin molding in thestator according to the second embodiment. FIGS. 2 to 5 will also bereferred to as appropriate.

The air-core coil 30 a is wound (ST301). The air-core coil 30 a is woundwith use of a winding frame (not illustrated), for example. The air-corecoil 30 a is wound in the shape of a rectangular frame and has thehollow air-core portion 31 at the center (see FIG. 2). The electric wireof the air-core coil 30 a is formed from a square wire with arectangular cross-section.

Then, the air-core coil 30 a is bent (ST302). Specifically, the air-corecoil 30 a is put into a molding die (not illustrated) and is shaped suchthat the cross section of the air-core coil 30 a is arc-shaped (see FIG.3). That is, the air-core coil 30 a is shaped to have an arc-shapedcross-section.

Next, the conductive pins 32 and 32 are brazed (ST303). The conductivepins 32 and 32 are brazed to the winding start portion and winding endportion of the air-core coil 30 a, respectively. Accordingly, the tipportions of the conductive pins 32 and 32 of the arc-shaped air-corecoil 30 a are exposed. Instead of soldering the conductive pins to thewinding start portion and winding end portion of the air-core coil 30 a,the winding start portion and winding end portion of the air-core coil30 a may be exposed.

Then, the first resin molding is performed to resin-mold a portion ofthe shaped air-core coil 30 a (ST304). The first resin molding isperformed in such a manner that a portion of the resin-molded air-corecoil 30 a constitutes a reference plane 30 b at the step of second resinmolding as second-time resin molding (see FIG. 10). Referring to FIG.10, the air core coil 30 a has an arc-shaped cross-section which has anouter arc surface 301, an inner arc surface 302 and side surfaces 303,304 connecting the outer arc surface 301 and the inner arc surface 302.The outer arc surface 301 includes a first portion 301 a, a secondportion 301 b, a third portion 301 c and a fourth portion 301 d.

When the air-core coil 30 a is set in a molding die for resin moldingwith reference to the insulating bobbin described above, the air-corecoil 30 a may not be pressed by the molding die and thus the air-corecoil 30 a may lift at ejection molding. This may bring about a moldingfailure, reduction in the yield of the molded coil 30, and deteriorationin dimensional accuracy of the molded coil 30. In this case, by formingthe reference plane 30 b at the step of the first resin molding, it ispossible to prepare the second resin molding. This leads to improvementin the yield and enhancement in the dimensional accuracy of the moldedcoil 30. At the step of the first resin molding, the air-core coil 30 ais sandwiched and fixed in the resin molding die at a predeterminedposition, and then is resin-molded. That is, the first resin moldingincludes sandwiching and fixing the air-core coil 30 a in the moldingdie at a predetermined position.

For resin molding at the step of the first resin molding, a low-thermalconductivity resin with high fluidity may be used. It is found that amotor's principal heat source is a coil. To release heat from the coilas a heat source, the resin covering the coil is preferably ahigh-thermal conductivity resin. However, the high-thermal conductivityresin is generally difficult to handle due to its low fluidity. Thus, atthe step of the first resin molding, the air-core coil 30 a is moldedwith use of a low-thermal conductivity resin having high fluidity tofacilitate production of the reference plane 30 b for molding at thenext step of the second resin formation.

Next, the second resin formation is performed to resin-mold the otherportions of the air-core coil 30 a with the reference plane 30 b(ST305). At the step of the second resin formation as the second-timeresin molding, the entire periphery of the air-core coil 30 a includingthe other portions not molded at the first resin molding is covered witha resin for insulation (see FIG. 11).

For the resin molding at the step of the second resin molding, ahigh-thermal conductivity resin may be used. As described above, toenhance performance of heat release from the coil as the motor'sprincipal heat source, molding can be performed with use of ahigh-thermal conductivity resin to efficiently release the heat. In theembodiment, first, at the first resin molding, a lowthermal-conductivity resin with high fluidity is used to resin-mold theair-core coil 30 a. Accordingly, the reference plane 30 b is formed withhigh dimensional accuracy. Next, at the second resin molding, ahigh-thermal conductivity resin is used to resin-mold the other portionsof the air-core coil 30 a with the reference plane 30 b. Accordingly, acoil-molded component with high dimensional accuracy and high heatrelease performance can be produced. In addition, at the second resinmolding, the resin-molded portion of the air-core coil 30 a (forexample, the reference plane 30 b) formed at the first resin moldingstep is sandwiched and thus the air-core coil 30 a is fixed in the resinmolding die at a predetermined position. This enables resin molding withhigh dimensional accuracy. Specifically, the second resin moldingincludes sandwiching the portion of the air-core coil 30 a resin-moldedat the first resin molding and fixing the air-core coil 30 a in themolding die at a predetermined position.

At ST305, the molded coil 30 with an arc-shaped cross-section iscompleted (see FIG. 11). The tip portions of the conductive pins 32 and32 are exposed at the molded coil 30.

Next, the molded coils 30 are arranged on the stator core 20, and theteeth 22 of the stator core 20 are inserted into the air-core portions31 of the molded coils 30 (see FIG. 5). Accordingly, the molded coils 30are stored in the slots 23 on the outer side of the annular portion 21(see FIG. 1). In addition, the molded coils 30 arranged on the statorcore 20 are fitted into the yoke 10. Further, the circuit board 40 isattached to the moiled coils 30. Specifically, while the circuit board40 is placed on the molded coils 30, the circuit board 40 is brazed tothe conductive pins 32 and 32. Accordingly, the stator 2 is completed(ST306).

According to the method for manufacturing the stator of the embodiment,it is possible to improve the dimensional accuracy and the yield of themolded coils 30. In addition, when being incorporated into the motor,the stator 2 can release heat to the outside. Therefore, according tothe embodiment, it is possible to provide the stator 2 with the propertyof reducing temperature rise.

Third Embodiment of Method for Manufacturing Stator in SubjectDisclosure

A method for manufacturing the stator according to the embodiment willbe described with reference to FIG. 12. FIG. 12 is a diagram fordescribing a process for a method for manufacturing the stator accordingto a third embodiment. FIGS. 2 to 5, 10, and it will also be referred toas appropriate.

The air-core coil 30 a is wound (ST401). The air-core coil 30 a is woundwith use of a winding frame (not illustrated), for example. The air-corecoil 30 a is wound in the shape of a rectangular frame and has thehollow air-core portion 31 at the center (see FIG. 2). The electric wireof the air-core coil 30 a is formed from a square wire with arectangular cross-section.

Next, the conductive pins 32 and 32 are brazed (ST402). The conductivepins 32 and 32 are brazed to the winding start portion and winding endportion of the air-core coil 30 a, respectively. Accordingly, the tipportions of the conductive pins 32 and 32 of the air-core coil 30 a areexposed. Instead of soldering the conductive pins to the winding startportion and winding end portion of the air-core coil 30 a, the windingstart portion and winding end portion of the air-core coil 30 a may beexposed.

Then, the first resin molding is performed (ST403). At the first resinmolding, the air-core coil 30 a is bent in such a manner that itscross-section is arc-shaped, and a portion of the air-core coil 30 a isresin-molded. Specifically, the air-core coil 30 a is put into a moldingdie (not illustrated) and is shaped such that its cross-section isarc-shaped (the air-core coil 30 a has an arc-shaped cross-section), andat the same time, a portion of the air-core coil 30 a is resin-molded.

At the first resin molding, a molding die capable of concurrentlybending and resin-molding the air-core coil 30 a (a molding die forconcurrently bending and resin-molding the air-core coil 30 a) may beused, for example. That is, the bending of the air-core coil 30 a andthe first resin molding may be performed with use of the same moldingdie.

The first resin molding is carried out in such a manner that a portionof the resin-molded air-core coil 30 a constitutes the reference plane30 b at the second resin molding as the second-time resin molding (seeFIG. 10). By forming the reference plane 30 b at the step of the firstresin molding, it is possible to prepare the second resin molding. Thisleads to improvement in the yield and enhancement in the dimensionalaccuracy of the molded coil 30. At the step of the first resin molding,the air-core coil 30 a is sandwiched and fixed in the resin molding dieat a predetermined position, and then is resin-molded. That is, thefirst resin molding includes sandwiching and fixing the air-core coil 30a in the molding die at a predetermined position.

For resin molding at the step of the first resin molding, a low-thermalconductivity resin with high fluidity may be used. It is found that amotor's principal heat source is a coil. To release heat from the coilas a heat source, the resin covering the coil is preferably ahigh-thermal conductivity resin. However, the high-thermal conductivityresin is generally difficult to handle due to its low fluidity. Thus, atthe step of the first resin molding, the air-core coil 30 a is moldedwith use of a low-thermal conductivity resin having high fluidity tofacilitate production of the reference plane 30 b for molding at thenext step of the second resin formation.

Next, the second resin formation is performed to resin-mold the otherportions of the air-core coil 30 a with the reference plane 30 b(ST404). At the step of the second resin formation as the second-timeresin molding, the entire periphery of the air-core coil 30 a is coveredwith a resin for insulation (see FIG. 11).

For the resin molding at the step of the second resin molding, ahigh-thermal conductivity resin may be used. As described above, toenhance performance of heat release from the coil as the motor'sprincipal heat source, molding can be performed with use of ahigh-thermal conductivity resin to efficiently release the heat. In theembodiment, first, at the first resin molding, a lowthermal-conductivity resin with high fluidity is used to resin-mold theair-core coil 30 a. Accordingly, the reference plane 30 b is formed withhigh dimensional accuracy. Next, at the second resin molding, ahigh-thermal conductivity resin is used to resin-mold the other portionsof the air-core coil 30 a with the reference plane 30 b. Accordingly, acoil-molded component with high dimensional accuracy and high heatrelease performance can be produced. In addition, at the second resinmolding, the resin-molded portion of the air-core coil 30 a (forexample, the reference plane 30 b) formed at the first resin moldingstep is sandwiched and thus the air-core coil 30 a is fixed in the resinmolding die at a predetermined position. This enables resin molding withhigh dimensional accuracy. Specifically, the second resin moldingincludes sandwiching the portion of the air-core coil 30 a resin-moldedat the first resin molding and fixing the air-core coil 30 a in themolding die at a predetermined position.

At ST404, the molded coil 30 with an arc-shaped cross-section iscompleted (see FIG. 11). The tip portions of the conductive pins 32 and32 are exposed at the molded coil 30.

Next, the molded coils 30 are arranged on the stator core 20, and theteeth 22 of the stator core 20 are inserted into the air-core portions31 of the molded coils 30 (see FIG. 5). Accordingly, the molded coils 30are stored in the slots 23 on the outer side of the annular portion 21(see FIG. 1). In addition, the molded coils 30 arranged on the statorcore 20 are fitted into the yoke 10. Further, the circuit board 40 isattached to the moiled coils 30. Specifically, while the circuit board40 is placed on the molded coils 30, the circuit board 40 is brazed tothe conductive pins 32 and 32. Accordingly, the stator 2 is completed(ST405).

According to the method for manufacturing the stator of the embodiment,it is possible to improve the dimensional accuracy and the yield of themolded coils 30. In addition, since a large portion of the stator 2 ismolded of a high-thermal conductivity resin, the stator 2 can releaseheat to the outside when being incorporated into the motor. Therefore,according to the embodiment, it is possible to provide the stator 2 withthe property of reducing temperature rise. Further, the manufacturingmethod in the embodiment has steps smaller in number by one as comparedto the steps of the manufacturing method in the second embodiment. Thisreduces the manufacturing costs.

Next, conventional stators illustrated in FIGS. 13 to 15 and the statoraccording to the embodiment will be compared with each other. FIG. 13 isa schematic view of a conventional stator with three slots and threecoils. FIG. 14 is a schematic view of a conventional stator with sixslots and three coils. FIG. 15 is a schematic view of a conventionalstator with six slots and six coils. As illustrated in FIGS. 13 to 15,the conventional stator has trapezoidal molded coils 230. The otherstructural elements of the conventional stator are given the samereference numerals as those in FIG. 1.

Decreasing the number of coils in the motor leads to reduction in costsfor wire winding and wire connection in the motor. For example, in thecase of a three-phase motor, the number of coils is preferably a minimumof three or six.

However, when the molded coils 230 with trapezoidal cross-sections areused, dead spaces 223 incapable of accommodating the coils are producedin the slots 23 as illustrated in FIGS. 13 to 15. The dead spaces 223decrease the coil density in the slots 23, and thus the motor efficiencyis reduced.

In particular, as illustrated in FIG. 13, when three slots are used, thecoil density is significantly deteriorated. Meanwhile, as illustrated inFIGS. 14 and 15, it is understood that, as the number of slots and thenumber of coils increase, the dead spaces 223 become smaller.

Thus, according to the stator 2 and the motor 100) in the embodiment,the molded coils 30 with widely arc-shaped cross-sections are stored inthe widely arc-shaped slots 23. In addition, the yoke 10 is fitted ontothe outer side of the molded coils 30 arranged on the stator core 20.

Therefore, according to the stator 2 and the motor 100 in theembodiment, the spaces in the slots 23 can be used most effectively withthe simple structure. As a result, it is possible to provide the statorand the motor that improve the coil density and enhance the motorefficiency.

Further, the electric wires of the air-core coils 30 a are formed bysquare wires with rectangular cross-sections. Accordingly, it ispossible to reduce costs for wire winding and wire connection, andprovide the motor of a small size at low cost.

A preferred embodiment of the present disclosure is described above.However, the foregoing description is intended only for illustration ofthe present disclosure, and is not intended to limit the technical scopeof the present disclosure to the foregoing embodiment. The technique ofthe present disclosure can be carried out in various modes differentfrom the foregoing embodiment without deviating from the gist of thepresent disclosure.

The molded coils 30 may be formed by resin molding such that only thetop portions of the conductive pins 32 and 32 are exposed to theoutside.

In addition, embodiments of the subject disclosure may be first to fifthstators, first motor, and first to fifth methods for manufacturing astator as described below.

The first stator includes: a stator core having a plurality of teeththat is radially protruded outward from an outer periphery of an annularportion; an air-core coil that is stored in a slot formed between theteeth by inserting and arranging an air-core portion in the teeth of thestator core; and a yoke that covers a circumference of the air-core coilstored on the stator core, wherein the air-core coil is shaped in such amanner as to have an arc-shaped cross section, and the arc-shapedair-core coil is entirely resin-molded while a winding start portion andwinding end portion of the air-core coil are exposed.

The second stator is configured such that, in the first stator, anelectric wire of the air-core coil is formed by a square wire with arectangular cross-section.

The third stator is configured such that, in the first or second stator,the air-core coil is a resin-molded coil that is formed by being fixedto an electrically-insulating bobbin to be resin-molded.

The fourth stator is configured such that, in the third stator, ends ofthe resin-molded coil are coupled to a circuit board, and the circuitboard is fixed with an electrically-insulating elastic body sandwichedbetween a bracket and the circuit board.

The fifth stator includes: a stator core having a plurality of teeththat is radially protruded outward from an outer periphery of an annularportion; an air-core coil that is stored in a slot formed between theteeth by inserting and arranging an air-core portion in the teeth of thestator core; and a yoke that covers a circumference of the air-core coilstored on the stator core, wherein the air-core coil is shaped to havean arc-shaped cross-section, and the arc-shaped air-core coil isentirely resin-molded while tip portions of conductive pins coupled tothe winding start portion and winding end portion of the air-core coilare exposed.

The first motor includes a rotor that is stored in any of the first tofifth stators to be spaced therefrom and is fixed to the circumferenceof a shaft pivotally supported at a bearing in a rotatable manner,wherein the rotor has a plurality of permanent magnets on the surface orinside of a rotor core.

The first method for manufacturing a stator is a method formanufacturing a stator including: a stator core having a plurality ofteeth that is radially protruded outward from an outer periphery of anannular portion; an air-core coil that is stored in a slot formedbetween the teeth by inserting and arranging an air-core portion in theteeth of the stator core; and a yoke that covers a circumference of theair-core coil stored on the stator core, the method including at leastthe step of shaping the air-core coil to have an arc-shaped crosssection and the step of resin-molding the entire arc-shaped air-corecoil while tip portions of the air-core coil are exposed, wherein, inthe step of resin-molding, the arc-shaped air-core coil is fixed to anelectrically-insulating bobbin and then is stored in a resin moldingdie.

The second method for manufacturing the stator is a method formanufacturing a stator including: a stator core having a plurality ofteeth that is radially protruded outward from an outer periphery of anannular portion; an air-core coil that is stored in a slot formedbetween the teeth by inserting and arranging an air-core portion in theteeth of the stator core; and a yoke that covers a circumference of theair-core coil stored on the stator core, the method including the stepof shaping the air-core coil in such a manner as to have an arc-shapedcross section, the step of exposing tip portions of the arc-shapedair-core coil, the step of first resin molding for resin-molding aportion of the air-core coil, and the step of second resin molding forresin-molding the other portions of the air-core coil.

The third method for manufacturing the third stator is a method formanufacturing a stator including: a stator core having a plurality ofteeth that is radially protruded outward from an outer periphery of anannular portion; an air-core coil that is stored in a slot formedbetween the teeth by inserting and arranging an air-core portion in theteeth of the stator core; and a yoke that covers a circumference of theair-core coil stored on the stator core, the method including the stepof exposing tip portions of the air-core coil, the step of first resinmolding for shaping the air-core coil in such a manner as to have anarc-shaped cross section and resin-molding a portion of the air-corecoil, and the step of second resin molding for resin-molding the otherportions of the air-core coil.

The fourth method for manufacturing the stator is configured such that,in the second or third method for manufacturing the stator, the air-corecoil is sandwiched and fixed in a resin molding die at a predeterminedposition in the step of first resin molding, and the portion of theair-core coil resin-molded in the step of first resin molding issandwiched and fixed in the resin molding die at a predeterminedposition in the step of second resin molding.

The fifth method for manufacturing the stator is configured such that,in the any of the second to fourth methods for manufacturing the stator,the air-core coil is molded by a low-thermal conductivity resin havinghigh fluidity in the step of first resin molding, and the air-core coilis molded by a high-thermal conductivity resin in the step of secondresin molding.

The foregoing detailed description has been presented for the purposesof illustration and description. Many modifications and variations arepossible in light of the above teaching. It is not intended to beexhaustive or to limit the subject matter described herein to theprecise form disclosed. Although the subject matter has been describedin language specific to structural features and/or methodological acts,it is to be understood that the subject matter defined in the appendedclaims is not necessarily limited to the specific features or actsdescribed above. Rather, the specific features and acts described aboveare disclosed as example forms of implementing the claims appendedhereto.

What is claimed is:
 1. A stator, comprising: a stator core having anannular portion and plural teeth that protrude radially outward from anouter periphery of the annular portion, the annular portion and theplural teeth being integrally formed with each other, the annularportion having a cylindrical shape; a molded coil that has an air-coreportion into which the teeth of the stator core are inserted and that isstored in a slot formed between the teeth of the stator core; and a yokethat covers a circumference of the molded coil stored in the slot of thestator core, wherein the molded coil has an arc-shaped cross-section,the molded coil includes a resin-molded portion and an exposed portionexposed at the molded portion, the resin-molded portion comprises: anair-core coil having the air-core portion at a center of the air-corecoil; a first resin covering a portion of the air-core coil; and asecond resin covering an entire periphery of the air-core coil includingother portions not covered with the first resin, the air core coil hasan arc-shaped cross-section which has an outer arc surface, an inner arcsurface and side surfaces connecting the outer arc surface and the innerarc surface, the outer arc surface includes first to fourth portionssurrounding the air-core portion, the first and second portions beinglonger than the third and fourth portions, the first and second portionsextending in a direction of an axis of the cylindrical shape of theannular portion, and the first resin covers a part of the first portionor the second portion of the outer arc surface and the first resinextends from the air-core portion to one of the side surfaces.
 2. Thestator according to claim 1, wherein the exposed portion is provided bya winding start portion and winding end portion of the air-core coil. 3.The stator according to claim 2, wherein the exposed portion is providedby tip portions of conductive pins soldered to the winding start portionand winding end portion of the air-core coil.
 4. The stator according toclaim 1, wherein an electric wire of the air-core coil is a square wire.5. The stator according to claim 1, wherein the molded coil is aresin-molded coil that is fixed to an electrically-insulating bobbin. 6.The stator according to claim 1, further comprising anelectrically-insulating elastic body between a circuit board coupled toan end of the molded coil and a bracket to fix the circuit board to thebracket.
 7. A motor, comprising: the stator according to claim 1; ashaft that is pivotally supported in the stator in a rotatable manner;and a rotor that is stored in the stator to be spaced from the statorand is fixed to a circumference of the shaft, wherein the rotor has arotor core and a plurality of permanent magnets that is arranged on asurface or inside of the rotor core.
 8. The stator according to claim 1,wherein the annular portion and the plural teeth are separate membersfrom the yoke.
 9. The stator according to claim 1, wherein an electricwire of the air-core coil has a rectangular cross-section.
 10. Thestator according to claim 1, wherein the first resin is a low-thermalconductivity resin and the second resin is a high-thermal conductivityresin.
 11. The stator according to claim 1, wherein the resin-moldedportion comprises a plurality of the first resins, the first resinsbeing arranged in parallel to each other in the direction of the axis.